A conventional wheelchair generally includes a pair of large wheels rotatably mounted on two opposite sides of the chair and a pair of front casters pivotally mounted on two front side portions beyond the two large wheels. For driving the wheelchair, a patient sitting on the chair should rotate two push rims each secured on an outer portion of the large wheel easily causing tiredness for a patient especially for a weak patient. An electric wheelchair may be driven by electric power, which however should require two driving motors respectively installed on two wheels of the wheelchair to probably have the following drawbacks:
1. Two driving motors require two controllers to be disposed on two armrests of the wheelchair, increasing load of the chair and increasing installation cost thereof.
2. For turning either rightwardly or leftwardly, only a single motor on a single (right or left) side is actuated to slow down the turning operation and to cause an unstable driving operation since the driving force acted by such a single-side motor is unbalanced.
The present inventor has found the drawbacks of a conventional wheelchair and invented the present central steerable driving means for a wheelchair.